Spinning fibers



May 1942- F. c. ATWOOD 2,283,169

SPINNING FIBERS I Filed May 13, 1939 INVENTOR ,4; ATTORNEYS the spinning of artificial fibe s Patented May 19, 1942 oFFicE SPINNING FIBERS Francis Clarke Atwood, Newton, Mass., assignor to Atlantic Research Associates, Inc., Newton-- ville, Mass, a corporation of Delaware Application May 13, 1939, Serial No. 273,433

9 Claims.

The present invention relates tothe manufac-.

ture of fibers, and more particularly to an imstep of spinning. the fibers to insure theirproduction with improved and uniform characteristics.

An object of my invention is to improve the step of spinning artificial fibers so that the fibers proved process and apparatus to be used in the v its scope, the spinning of artificial fibers generally. V

In accordance with the preferred method of my invention, the composition from which the fiber is made is prepared by dissolving. casein,

either from a vegetable source such as soya beans or an animal source such as milk, in a liquid produced are uniformly free from brittleness have increased tensile strength and flexibility, and possess a softness which is comparable to that of the simulated natural fiber.

Another object of my invel afion is to improve that the fibers produced will be free from deleterious impurities which tend in time, and under ordinary conditionato bring about an undesirable discoloration of the'fibers.

A further object of my invention is toprovide an apparatus for accomplishing the above objects, and which can be formed from inexpensive, Y

easily workable material, whereby the same may be constructed in a convenient and economical fashion.

Still a further objectof my invention is to provide a spinning apparatus in which the spinwith the assistance of a .dispersingagent. The

casein solution thus'prepared and having a desired viscosity is extruded through fine orifices in a spinnerette immersed an acidic coagulating bath. A substantial amount of sulfuric acid is in such a manner contained in the bath, together with other reagents which advantageously may be present in the bath, such as sodium sulfate and the general class of casein hardening alums, i. e., potassium aluminum sulfate, and aluminum sulfate. The

extruded casein solution, upon. contact with the coagulating bath, receives an initial coagulation,

thus producing filaments which may be continuously withdrawn from the bath. In ordeifithat nerette comprises a metal from which it may be formed with greatfacility andhaving sufficient toughness whereby the spinnerette will not suffer abrasion at the orifices during the spinning operation, but which metal would dissolve in the fibercoagulating bath and injure the fibers-were it not for the prevention ofthe dissolution of the metal and consequent harm to the fiber;

An additional object of my invention is to prevent dissolution in the fiber coagulating bath of a spinnerette made of a metal normally harmful to the fibers, by contacting the spinnerette in the fiber coagulating bath with a metal which dissolves in preference to the metal of the spinnerette, and which dissolving metal upon solu-. tion. forms a salt which is less injurious to the the fibers may be completely and uniformly coagula'ted throughout their entire cross-section, itis necessary to permit the fibers "to remain in I the coagulating bath or to be kept wet with coagulating liquid that normally adheres t'o'them for a substantial period of time.-

The solution or dispersion of the casein that is extruded from the spinnerette into the coagulating bath is probably in the form of a caseinate, which upon contact with the acid is recon-.

verted into casein. This involves an interaction between the spun fiber and the acids and hardening ingredients of the bath. The complete coagulation of the fiber requires the ingredients of the coagulating bath to react with or become intimately admixed with-the-fiber. y.

I have discovered that the casein solution to be extruded should be free from such heavy metals as iron, manganese, and particularly copper and their salts, because the presence of even minute amounts of these materials in theextruded fibers fibers and which, preferably,'is a desirable, or at least a harmless, ingredient of the coagulating bath.

My invention is illustrated in the accompany ing drawing in which the single figure is adiagrammatic illustration partly in section and partly in elevation. Y

Although I will describe my invention more particularly with reference to the spinning, of synthetic protein fibers made, from casein, it will be apparent to, one skilled in the art that my invention is applicable to, and includes within imparts undesirable characteristics to them. The copper present in ionized form should not exceed one part in one million and preferably ,one part in twentyfmillion, while active iron should preferably be present in not over one part in two hundred thousand.

One of the deleterious effects of the presence of these impurities in the fiber, for example, is

the rendering of the fiber undesirably brittle.

Fibers containing such heavy metals, when contacted with a sulfide, alsoexhibit an undesirable dark color characteristic of heavy metal sulfides,

thus indicating that heavy metals have been deposited in the fibers. It will be appreciated that sulfides are not only present in the atmosphere as gases, but are found to a much greater extent in water and washing compounds. It is to be expected that fibrous material containing such heavy metals and/or their salts after a lapse of time and particularly upon laundering, will exhibit an undesirable discoloration.

I have also discovered that the presence of a small amount of the heavy metals or their salts in the coagulating bath has a similarly damaging effect upon the fibers being produced. It is believed that the prolonged and intimate conand that this occurs substantially as effectively.

as though the impurities were present in the original casein solution.

By a careful selection of pure ingredients and mixing the same undercontrolled conditions, it is possible to formulate an initial casein spinning solution which contains a very small or an insignificantamount of the undesirable impurities of the type discussed above. It is not so simple to employ a non-contaminating coagulating bath, because due to itsacidic nature, the bath dissolves any contacting parts fabricated -of heavy metal. a

It has been usual heretofore, to form the tank containing the coagulating bath of some inert non-metallic material, such as stone'or wood and the like. Attempts have also been made to fabricate spinnerettes from relatively inert metals such as tantalum, platinum or gold in order to prevent their solution,but such materials are generally avoided because such inert metals, as a rule, are

extremely soft and often difficult to solder, with the result that a spinnerette of a desired design can be fabricated only with great dimculty. An- -other inherent disadvantage in the use of soft metals is that the abrasion of the spinnerette orifices by the extruded solution rapidly enlarges and distorts the orifices with the result that a uniform fiber and one of desired cross-sectional dimensions and form cannot be produced and the V spinnerette must ,be frequently replaced. Moreover, such materials are relatively costly and greatly increase the expense involved in the process.

Materials which are inexpensive, relatively tough, and from which aspinnerette can be read- -ily formed, such as brass, would be ideal'from the manufacturing or economic point of view, as well 'as because a spinnerette formed of such-- metal would retain its orifice dimensions without appreciable abrasion by the extruded solution. I have observed, however, that when such apparatus is utilized in the step of spinning artificial fibers, the fibers being produced exhibit the characteristic brittlenessof fibers containing undesirable metal impurities, and the presence of such impurities may be further evidenced by the sulfide test discussedabove. Careful weighing of the spinnerette and supporting apparatus shows that they have suffered a decrease in mass which may be correlated to the undesirable results being obtained.

I have pointed outheretofore that in the case of spinning synthetic fibers from casein, there are certain metals, such as aluminum, which in the form of their salts are desirable addition agents in the coagulating bath. I have also discovered that there are certain metals, such as zinc, which when present in the bath in the form of their salts, exert in some cases, an apparent beneficial effect upon the synthetic fibers produced, and in general have at least no appreciable detrimental effect. But aluminum and other soft metals such as, zinc, are not suitable for use in forming a spinnerette because the same would corrode rapidly, particularly at the orifices, with the result that frequent replacements would be necessitated.

It is apparent that the various metals may be evaluated and listed in accordance with the effects they produce upon the characteristics of the extruded fibers when present as salts in the coagulating bath. In the spinning of casein fibers, for example, the metals will range from those producing a decidedharmful effect such as, copper, manganese,- and iron, to those exerting a highly beneficial effect such as aluminum. The comparative rating to be given a particular metal will depend on the fibers being produced.

In accordance with my invention, I employ a spinnerette made from a metal which normally is readily workable and which is harmful in the bath, but I avoid contamination of the coagulating bath by electrically coupling the spinnerette with a member formed of a metal or metals which have a less harmful. effect and, preferably, are a beneficial or at least a harmless ingredient in the bath, and which coupling metal dissolves in the bath rather than the metal of the spinnerette'. In order. to prevent the dissolving of meatl of the spinnerette and to accomplish this at the expense of the solution of the metal forming the coupling member, it is necessary to have said member electropositive with respect to the spinnerette. some confusion exists as to the proper terminology to be employed, and I prefer to designate as "electropositive the member of the system which is anodic and tends to pass into solution.

The simplest form of my invention is in the use of an electric couple in which the metal forming the protecting member is selected from the group of metals which, because of their electrolytic potential values, areinormally electropositive with respect to the spinnerette metal. The electrolytic potential relationship between the various metals may be readily ascertained by. reference, to any standard table. Aluminum,

magnesium and zinc are particularly desirable for forming the protecting member inasmuch as they are all relatively highly positive with respect to hydrogen, The selection of a particular metal will depend, of course, on the fiber being pr duced.

It will be apparent that when the spinnerette f metal is selected from a lower position in the electrolytic potential table, the group of metals which maybe used for protective purposes correspondingly increases.

In a particular embodiment of my invention as'applied to the spinning of, synthetic protein fibers from casein, a b'ras's spinnerette may be nent of brass, namely, 0.34 volt for copper, (all potentials referred to hydrogen as zero). As a result of these potential difierences, the spinnerette metal does not appreciably pass into solution. Under certain conditions, a zincsupporting bracket may be substituted for the aluminum bracket described above with satisfactory results. The zinc couple efiectively prevents the solution of copper from the spinnerette.

In the above engaodiment, the couple has been described as one i which the aluminum or zinc is present in the form of a supporting bracket for the spinnerette, but it is to be understood that a couple\in this formismerely for convenience, and that, if desired, the protecting member may be constructed independently of all or part of the apparatus used in spinning fibers. It is essential only that the protecting member be in contact with the coagulating'liquid and \in contact with or otherwise electrically con-v i nected to the spinnerette. An advantage in forming the protecting member independently of the' spinning apparatus, is that'the utilization of an implied E. M. F. as disclosed hereinafter is facilitated.

If desired, the spinnerette may be plated with a metal which is less reactive with an acidic coagulating bath than is themetal from which the spinnerette is formed. In the case of a'brass spinnerette, for example, the same may be conveniently platedwith nickel, gold or silverby the electrodeposition process. In the case of gold or silver, the same may be amalgamated to include mercury within the protecting coating.

A metal such as nickel or mercury is not reactive with an acidcoagulating bath probably be-;

cause of its normal passivity or because of the normal high overvoltage of either oxygen or hydrogen when plated out thereon. This high overvoltage efiectively counteracts .the electrolytic potentialnormal to these metals. The protective value of a plate formed of noble metal, such as gold, is the result of the well known chemical.

inertne'ss of these metals. The protecting mem' ber ,couple, discussed above, is utilized in combination with a plated spinnerette, primarily -for preventing contamination of the acid coagulating bath by the exposed portions of the metal from which the spinnerette is formed, particularly "at the orifices thereof.

In the drawing the coagulating bath 2 is contained in a tank I, in which coagulating bath a spinnerette 4 is immersed. The metal of the spinnerette 4 is cathodic with respect to the protecting member 3 or the support 5, or both,

as has been described heretofore.

A further variation in the embodiment of my invention is to separate the spinnerette from theprotecting memberso that a small potential from an outside source may be impressed across the spinnerette and the member. This potential may be utilized to augment a normal positive potential of the protecting member with respect to the spinnerette due to their electrolytic potential values, or to cause the protecting member to be anodic with respect to said spinnerette where the electrolytic potential values are substantially equal or the spinnerette is normally anodic relative to the protecting member.

It will be appreciated that in forming agulating solution or the casein solution from materials of ordinary commercial purity, the solutions will almost always contain initially a small but undesirable percentage of copper and iron or other heavy metals. It is an advantage the 00- of my invention that the protecting member will also act to purge the solutions of 'these minute quantities of undesirable heavy metals by electrolytic deposition 1. e., the impurities will plate out and be replaced by the'metal forming the protecting member, The purging efiect'with respect to the casein solution is more pronounced when the protecting member contacts the solution prior to its extrusion andcoagulation'into synthetic fibers. 5 I

It is understood that the use of electric couples. and the like is well known in the electrochemical art, but there has been no appreciation of a the following claims.

the fact that electrochemical principles could be' applied to the art of spinning artificial fibers to prevent the formation of ions in, the coagulating bath which adversely affect the characteristics of, thefibers being produced, in favor of the- I claim:

1. An apparatus for spinning synthetic fibers comprising a spinnerette formed ofa metal which normally dissolves inan acidic coagulating liquid with deleterious effects upon synthetic fibers .co--

- agulated therein, and a protecting member eleclated therein, and a protecting member electrically connected to the spinnerette and formed of a metal which upon solution in an acidic coagulating liquid has a less deleterious effect upon synthetic fibers coagulated therein than that result-ing irom the solution of the spinnerette metal, said protecting member being anodic with respect to said spinnerette, whereby during contact of the spinnerette and the protective member with an acidic coagulating bath, the protective member dissolves instead of the spinnerette.

2. An apparatusfor spinning synthetic fibers comprising a spinnerette formed of a metal which normally dissolves in an acidiccoagulating liquid with deleterious effects upon fibers being coagu-- trically connected to said spinnerette and' formed ofa metal which exerts a less deleterious'efiect when dissolved in an acidic c agulating liquid upon the fibers being'coagulated. therein than that resulting from the solution of the spinnerette metal; the metal of the protecting member .being anodic withrespect to the spinnerette metal whereby it dissolvesinstead of the spin- .nerette when the spinnerette and the protective member are in contact with an acidic coagulating bath;. 4 v

3. An apparatus for spinning synthetic protein fibers which are harmed during the spinning operation by contact witha solution containing certain heavy metals, comprising a container for holding an acidic solution containing a metal salt that exerts a beneficial action in the coagulating of the'fibers, a spinnerette within said container adapted to be immersed in the acidic coagulating solution. and formed of one of said heavy metals which normally dissolve in the coagulating solution to exert said harmful action upon the protein fibers being produced, and which resist abrasion during the spinning operation, and a protecting member also within the container electrically connected to said spinner- 'ette and also adapted to contact the coagulating liquid, said protecting member being formed of a metal which'upon dissolving in the coagulating solution forms a salt that is present in said solution and exerts said beneficial action upon the fibers, said metal of the protecting member also being anodic with respect to the metal of said spinnerette whereby it dissolves in prefer- =nce to the metal spinnerette. g

4. An apparatus for spinning synthetic protein fibers in an acidic'coagulating bath, comprising a brass spinnerette and an aluminum protecting member electrically connected thereto,

said spinnerette and protecting member being adapted to be immersed in said acidic coagulating bath during the spinning operation,-

whereby the aluminum dissolves in the bath in preference to the brass.

5 pparatus for spinning syntheticfibers in an acid coagulating bath containing an aluminum salt, comprising a brass spinnerette and an aluminum supporting bracket therefor electrical- 1y connected to the spinnerette, said spinnerette and support being adapted to be immersed in said acidic coagulating bath during the spinning operation, whereby the aluminum dissolves in the bath in preference to the brass.

6. An apparatus for spinning synthetic fibers in an acidic coagulating bath, comprising a spinnerette formed of copper-containing metal, and a metallic protecting member electrically connected thereto, said protecting member being anodic with respect to copper whereby the metal of said protecting member dissolves in the'bath in preference to the copper.

7. In a method ofspinning artificial fibers Y egaaaieo tecting member is formed of metal which upon solution in the acidic coagulating bath has a less deleterious efiect upon the fibers than thatproduced bya solution of the harmful metal in the spinnerette and which protecting member is anodic with respect to said spinnerette, whereby theccoagulating bath tends to dissolve the metal of .the protecting member in preference to the.

metal of the spinnerette.

8. In a method of' spinning artificial fibers from material that is extruded through the oriflces of a spinnerette into an acidic coagulating z bath, which material is harmed by contact with a coagulating bath containing certain heavy metals in solution, the prevention of contamination of saidbath by a spinnerette formed of at least one of said harmful metals which is in contact with the acidic bath by maintaining a protecting member electrically connected to said spinnerette and in contact with the bath, which protecting member is formed of metal which upon solution in the coagulating bath has a less deleterious eifect upon the fibers than that produced by a solution of the harmful spinnerette 'metal, and which also is anodic with respect to the metals of said spinnerette, whereby the co-. agulating bath tends to dissolve the metal of the protecting member inpreference to the metal of the spinnerette.

9. In a method of spinning synthetic protein fibers from a casein solution that is extruded through a brass spinnerette into an acidic coagulating bath containing aluminum salts, which solution is harmed by contact with a coagulating bath containing dissolved copper, the prevention of contamination of said bath by the brass spinnerette immersed in said acid by maintaining the brass spinnerette in electrical contact with an immersed aluminum protecting member,

whereby the coagulating bath tends to dissolve the aluminum of the protecting member in pref: erence to the brass of the spinnerette.

FRANCIS CLARKE ATWOOD. 

